Due to its reduced weight (typically 50%) and increased durability, carbon-reinforced silicon carbide (CSiC) ceramic composite offers a best-in-class alternative to traditional iron or cast iron brakes. However, the application of CSiC brake discs has remained the preserve of the mainstream high-performance OEM market, primarily due to the high unit cost but also due to the re-engineering normally associated with employing CSiC brakes. This is because ceramic composite brake discs generally need to be of a larger diameter to provide comparable performance to a cast iron brake system. This requires significant re-engineering of the brake components, wheels and related areas to accommodate the larger brake disc. This has limited the adoption of CSiC brakes for small volume or niche applications as these engineering costs, combined with the high tooling costs for any new design, make the technology unattractive.

Scope

This project aimed to simplify the re-engineering process in moving from cast iron to CSiC discs by replacing the cast iron brake
discs with CSiC brake discs of the same dimensions. To account for differences in specific heat capacity and density a larger CSiC disc is generally required to replace an iron disc to achieve a similar thermal mass and hence similar performance. The material properties of the continuous fibre construction allow a disc of the same dimensions to have comparable thermal performance, providing the potential to replace a cast iron disc on a like-for-like basis.

The project therefore focused on CSiC brake discs made with continuous fibre construction.

The project was part-funded by the Niche Vehicle Network and was undertaken in conjunction with Briggs Automotive Company (BAC) Ltd. The project aimed to improve the standard braking system on their supercar, the BAC Mono.

Image 2 – The BAC Mono Supercar

The target was to maintain the existing hub, caliper and other brake components, to keep costs down and minimise re-engineering. A secondary aim was to reduce the weight of the brake disc even further and investigating the impact on performance of increased diameter
cooling vents.

Chopped Fibre vs. Continuous Fibre

Chopped-Fibre is the standard material used in the construction of the CSiC d iscs found on many high performance vehicles, such as Ferrari, Porsche and Aston Martin. This material consists of carbon-fibre cut into short strands and mixed with a resin.

Continuous fibre material is made from layers of Poly-Acrylic Nitrile (PAN) cloth, a carbon-fibre pre-cursor, that are laid over each other (typically in a 0°/90° layup) and needled together to produce a matrix structure. The final product generated by each process are similar, however the Continuous Fibre material benefits from higher strength and significantly higher thermal conductivity.

The thermal conductivity of ST's high conductivity material is typically 3 times that of the chopped fibre material. The manufacturing process of continuous fibre is also more suited to small volume or niche vehicle applications as the parts are machined as opposed to Chopped Fibre discs that are moulded. This results in minimal tooling costs and greater flexibility in production.[/b]

As the project aim was to replace an existing cast iron disc with a CSiC disc, the basic dimensions; outer diameter, inner diameter and thickness were defined by the original disc. However the design of the cooling vents
was not fixed and as such it was decided to produce two different designs, the first with 8mm radial cooling vents and a second with larger 12mm vents. Table 1 shows a comparison of the key dimensions between the different designs.

Table 1 – Comparison of key dimensions and weight

Both CSiC discs were manufactured by Surface Transforms at their UK plant using continuous fibre material and assembled with aluminium bells using a fully-floating fixing system of ST’s own design.

Disc Mass Verification

Surface Transforms has developed a brake disc sizing tool through dynamometer and vehicle testing which is used to verify the mass
of ceramic brake discs for specific applications. The principle of the calculation is based on the temperature rise due to transferring the kinetic energy of a vehicle into thermal energy in the disc using its heat capacity.

There are two aspects to the thermal calculation;

1. A single stop from the vehicle maximum velocity. This takes no account of any cooling effects or heat loss in the system.

2. A set of multiple stops from maximum velocity with no cool-down time between stops. This makes some assumptions about heat loss in the system, determined using dynamometer test results which remain conservative.

Each disc design was assessed using this technique to verify that it has sufficient thermal mass for the application without exceeding a recommended maximum operating temperature of 650°C.

The predicted temperatures can be found in Table 2.

Table 2 – Predicted brake temperatures

The maximum temperature limit calculated using this tool is 500°C to allow for a margin of safety below the 650°C material limit. The above figures showed that the discs were sized correctly for the application. It is important to state that these calculations do not take into account the cooling vent design.

Disc Strength Verification

A structural analysis was performed on the bell and the disc to confirm that the assembly design was strong enough to safely handle the
expected operating loads.

The force experienced by each mounting bolt hole of the disc when stopping from maximum velocity was calculated. This load was then used in a FEA simulation.

The strength of the bell was then investigated using the same process.

Image 5 – FEA simulation of the bell design

The predicted stresses in both components were demonstrated to be well below the yield strength of the material.

Dynamometer Testing

A comparison of the relative brake performance between the cast iron disc, CSiC disc with 8mm radial cooling vents and CSiC disc with 12mm radial cooling vents was performed on ST’s brake dynamometer based at Birmingham City University. The following braking attributes were tested after an initial bedding-in procedure had been performed:

1. Fade
2. Pressure sensitivity
3. High velocity performance

Typical AK master fade tests resulted in similar peak temperature between all three discs, ranging from 463°C to 470°C. Both CSiC discs reached significantly lower temperatures between braking operations than the cast iron disc, demonstrating improved cooling performance. This improvement was most significant with the CSiC disc with 12mm radial cooling vents (see Graph 1).

During pressure sensitivity testing all discs behaved in a similar manor, showing minor variations in coefficient of friction values at various brake line pressures. The cast iron disc had a noticeably greater noise and vibration at low pressures. Comparable to the fade test, all discs achieve a similar peak
temperature but the ceramic discs dropped to lower temperatures between stops.

In the high speed stops it is possible to see once again that the ceramic brake discs cool down faster between stops to reach a lower temperature.

Conclusion

Dynamometer testing demonstrated that a CSiC brake disc with continuous fibre construction can achieve the same thermal performance as a cast iron disc allowing for a like-for-like replacement whilst achieving a weight reduction in excess of 50%.

Testing also demonstrated that careful cooling vent design can allow for a reduction in mass without compromising the thermal performance of the CSiC disc. A potential reduction in mass of CSiC brake discs used for other applications can also be explored with far greater confidence as a result of this testing.

It is envisaged that the results of this project, along with additional testing, can be used to develop a revised brake disc sizing tool which also accounts for cooling vent design and can therefore support the production of CSiC discs with further increased efficiency.

Whilst the carbon-ceramic discs you find on production road cars conventionally use discontinuous (chopped) carbon fibre, ST interweaves continuous carbon fibre to form a 3D multi-directional matrix, producing a stronger and more durable product with 3x the heat conductivity of standard production components, this keeps the brake system temperature down and the brake performance consistent.

Surface Transforms has developed unique patented next-generation Carbon-Ceramic Technology that provides the ultimate braking performance for road and track. Here’s just seven reasons why you need this technology on your vehicle –

Surface Transforms uses a unique patented process to produce it's carbon-ceramic material, whilst we can’t tell you all our secrets we can give you an overview of how the discs are made.

Stage 1 - Carbon Fibre Preform
A unique 3D structure of carbon-fibre is weaved together from multiple layers of carbon-fibre cloth to form the base carbon material (pre-form).

Stage 2 – Carbonisation
The carbon pre-forms are heated to a temperature of (1,000-3,000° C) in a furnace filled with a gas mixture that does not contain oxygen. The lack of oxygen prevents the carbon from burning in the very high temperatures. As the pre-forms are heated, they begin to lose their non-carbon atoms, plus a few carbon atoms, in the form of various gases including water vapor, ammonia, carbon monoxide, carbon dioxide, hydrogen, nitrogen, and others. As the non-carbon atoms are expelled, the remaining carbon atoms form tightly bonded carbon crystals that are aligned more or less parallel to the long axis of the fibres.

Stage 3 – Chemical Vapour Infiltration (CVIST)

Surface Transforms have developed their own process CVIST based on the Chemical Vapor Infiltration method of Ceramic Matrix Composites fabrication. This is a process in which reactant gases diffuse into the porous preform and form a deposition. Deposited material is a result of chemical reaction occurring on the fibers surface. The deposition fills the space between the fibres, forming composite material in which matrix is the deposited material and dispersed phase is the fibres of the preform.

Stage 4 – Heat Treatment
Following CVI, the parts are placed in a furnace and taken through a further cycle at very high temperature.

Stage 5 – Green-State Machining
At this stage, the parts are solid blanks of close to the finished dimensions but not yet as hard as the final part. Most of the machining of the component features is done at this stage, as machining after the next stages is expensive and time consuming due to the high hardness of the material.

Stage 7 – Final Machining
A final machining process is required to achieve the specific tolerances required for brake components.

Stage 8 – Anti-oxidant coating
Before parts are completed, an anti-oxidant coating is added to reduce oxidation and increase the life of the part.

Stage 9 – Inspection
A CMM (co-ordinate measuring machine) inspection of each part along with DTV (disc thickness variation) measurements is performed to ensure all parts meet the strict tolerances required by our customers.

Stage 10 – Despatch
The final parts are packaged in our Surface Transforms bespoke shipping boxes and despatched by courier to our customers around the world.

At the IAA in Frankfurt in 1999, the carbon-ceramic brake disk had its world premiere. The use of the high-tech material had revolutionized the brake technology: In comparison to the conventional grey cast iron brake disk the carbon-ceramic brake disk weighed round 50 per cent less reducing the unsprung mass by almost 20 kilograms. Further significant advantages are: improved brake response and fading data, high thermal stableness, no hot judder, excellent pedal feel, improved steering behavior, high abrasion resistance and thus longer life time and the advantage of avoiding almost completely brake dust. At first Porsche AG built the carbon-ceramic brake disk in 2001 into the 911 GT2 as series equipment. Since that time also other premium brands use the advantages of this innovative brake technology for more security and comfort. These are for example sports cars and luxury class limousines from Audi, Bentley, Bugatti and Lamborghini.

Dimensioning and Design

The overall car braking system is designed to match a car´s layout and take advantage of the ceramic brake disk material´s properties. We cover the designing of the brake – the construction of the brake disk as well as the selection of the friction layers and the caliper – and adjust the brake into the concept of the vehicle. The main parameters determining the braking system design are a car´s maximum speed, the time sequence of full brake applications possible to bring a car to a stop from top speed and the mass to be braked, in addition to the axle load distribution and the car´s aerodynamics. The purpose of brake disk dimensioning and design is to ensure that a car can be stopped safely under any conceivable driving conditions. Braking system design also needs to ensure that neither the disk itself nor any other component in its direct vicinity is exposed to excessive thermal loads. The optimal cooling vane geometry is determined by numerical methods (Computational Fluid Dynamics) for each car model. The design calculation also takes account of the air pressure building up underneath the car and inside the wheel arch as a function of the car´s aerodynamic design and traveling speed.

Material

A special feature of carbon-ceramic brake disks is the ceramic composite material they are made from. Both the carbon-ceramic brake disk body and the friction layers applied to each side consist of carbon fiber-reinforced silicon carbide. The main matrix components are silicon carbide (SiC) and elemental silicon (Si). The reinforcement of the material is provided by carbon fibers (C). Silicon carbide, the main matrix component governs great hardness for the composite material. The carbon fibers make for high mechanical strength and provide the fracture toughness needed in technical applications. The resulting quasiductile properties of the ceramic composite material ensure its resistance to high thermal and mechanical load. Carbon fiber-reinforced silicon carbide materials thus combine the useful properties of carbon fiber-reinforced carbon (C/C) and polycrystalline silicon carbide ceramics. The elongation at break of C/SiC materials ranges from 0.1 to 0.3%. This is exceptionally high for ceramics. The entire characteristic profile makes fiber-reinforced silicon carbide to a fist-choice material for high-performance brake systems: Particulary the low weight, the hardness, the stable characteristics also in case of high pressure and temperature, the resistance to thermal shock and the quasiductility provide long live time of the brake disk and avoid all problems resulting of loading, which are typical for the classic grey cast iron brake disks.

The secret of the advantages of the carbon-ceramic brake disk is the unique production process over approximately 20 days. To produce carbon-ceramic brake disks, we use carbon fibers which are given a special protective coating and then cut into short fiber sections of defined thickness and length. The production process includes preparation of the fiber mixture, the production process for the disk body and the bell mounting as well as the final machining of the assembled brake disk. The entire production process is monitored with various tests and ends with one final testing. The production process of the ceramic brake body continues with a preform pressed with binding resin to a so called green body which will be converted in the ceramic component by carbonizing at 900 °C and siliconizing at 1700 °C in high vacuum. The complex feature of the manufacturing process is the use of the “lost core” technology – a plastics matrix which defines the design of the cooling vane geometry and which burns out without residues at carbonizing – as well as the different fiber components of the brake disk body, the friction layers on the ring exterior side and the point-shaped abrasion indicators which are integrated into the friction layer.

Product Development

A carbon-ceramic brake is developed in three main stages to match a car´s particular layout: numerical modeling, the construction and testing of prototypes, and testing on an actual car. The brake disk is first simulated numerically on the computer, using the car´s particular model data. The carbon-ceramic brake disk´s diameter, its thickness and the height of the friction path are only some of the parameters calculated on the computer. Calculations for assembled carbon-ceramic brake disks include the design of the bell connection. This is a highly demanding design task because of differences in coefficients of thermal expansion need to be compensated for at any operating temperature possible. The numerical model also provides the design of the cooling vanes configured to optimise fluid dynamics. In the second development stage, prototypes (test specimens) of the carbon-ceramic brake disks are constructed on the basis of numerical model results and bench-tested, together with the matching brake pads and calipers. In the third and final stage, the disk prototypes are tested on the car. They complete not only high-speed runs on a test circuit but also mountain pass descents and road tests. On these test runs, the driver evaluate brake behavior, in particular braking performance and braking comfort, and the computer provides a detailed analysis of measured results. Together with the bench test results, the car test runs determine whether a disk prototype can be approved or not.

Quality Assurance and Testing

The braking system is the most important safety system in any car. Carbon-ceramic brake disks therefore need to be manufactured to consistently high quality standards. This is why we have introduced a comprehensive Quality Management System conforming to VDA 6.1 and ISO 9001:2000. The system describes all production and operating processes and also ensures the consistent monitoring and documentation of product quality – from the raw material used to the finished product. The Manufacturing Execution System and a Computer-Aided Quality System are used to implement it. We record all production data and test results for each individual carbon-ceramic brake disk. This allows each disk to be identified both during production and also later when the disk has been mounted on the car. All operations concerned are documented in an Enterprise Resource Planning System and a CAQ System, together with all tests and inspections, the staff and equipment involved, and the results of the tests. Each carbon-ceramic brake disk thus generates around 600 data items during its complete production run.

Automotive Racing Products: Carbon/Carbon (C/C) brakes are at their premium performance levels in high energy situations. They have outstanding thermal shock resistance, do not fade, offer consistent brake performance, are light weight and wear resistant. The brake rotor and pads are made entirely from C/C as it provides both structural and frictional properties.

We developed the first automotive racing application of Carbon/Carbon brakes for Formula One teams. Today we utilize the focused concept to develop and produce friction products for a growing list of customers on the move. This concept concentrates our expert personnel and production equipment to support existing and new friction products and customers, optimizing throughput and service while minimizing costs. Our world-class product offering includes brakes, clutches and other friction products for aircraft, trains, trucks and automobiles.

Sicom claims that in 20 days they will refurbish your worn pccb to "better than new" (not sure what that means) for 795 Euros... anyone tried this before?

SICOM Refurbishment

This is a worldwide exclusive service by SICOM/Foxx Automotive

surface revitalization of worn ceramic brake rotors
guaranteed quality standards by SICOM by X-ray and weight check of every rotor
refurbishing rotors passing our production process for carbon ceramic rotors and will get the same ultrahard friction surface as our premium rotors
final quality check by scaling and balancing control

....after

The refurbishing process in detail:

After the initial incoming control the discs are weighed and depending on wear and wear pattern the rotors are x-rayed and examined for structural damage.
After that any brake pad residue or contaminates is chemically steamed off
The rotors are machined until they are level
The napped are vacuum soaked in polymeric carbon
The next step is to pyrolyze the rotors at 1100°C
The last two steps are repeated three times
now the discs are siliconized at 1500°C
The top layer ( ca. 1mm thick ) is now restored, and trough the pyrolysis it is chemically and physically bonded with the structure
Now follows the final sanding of the top layer
The disc is completely reassembled and is weighed once more and precision-balanced
The disc now has gained about 30-50g and is at desired value once more

So, if companies like this can fix pccb's.. a lot of the fear of ordering pccb because of porsche's replacement cost should be eliminated no?

The possibility was evaluated based on our understanding from various CCM OE applications. We are not sure how reliable those marketing material are but since you brought it up please allow us to comment on those claimed "advantage"

RB CCM rotor/brake kit design is based on our extensive research and understanding from various OE CCM applications, and joint efforts with ST (Surface Transforms) who supplied the CCM-X discs and successful CCM brake deployment for GT-R.

For those who are interested in learning more; including the difference between Brembo and Surface Transforms, may refer to this link in RB forum.

Share with you is a research I have done for our CCM brake development.

I have been reading hundreds of threads in this and other forums about "pccb" or not "pccb" or something to that nature and for sure many more to come but I have yet seen a fact sheet comparing these two type of rotor materials:

This chart with my comment and note should satisfy most of your query for a clear and true understanding between two type of rotor material, and their respective advantage and disadvantage which hopefully can help you make a better decision.

Analysis is based on the data published by SGL (Now owned by Brembo) and my reference from various material data book. My comment was duly verified by Geoff Whitfield - Engineering Manager of Surface Transforms.

This presentation is deemed to be accurate at the time of publishing.

If you still have question please feel free to address, in the meantime please keep the discussion focused on the material fundamental and their respective characteristics.

For those who are interested in learning more, we have a more comprehensive collection on CCM including mfg process and experiment data etc. here:

Brake Burnish Procedure
1. Apply the brakes 4 times starting at 50 mph (80 km/h) to 20 mph (30 km/h) while decelerating at 0.3 g.
2. Cool the brakes while driving 50 mph (80 km/h) for 3 minutes.
3. Apply the brakes 6 times starting at 90 mph (145 km/h) to 20 mph (30 km/h) while decelerating at 0.5 g.
4. Cool the brakes while driving 50 mph (80 km/h) for 3 minutes.
5. Apply the brakes 10 times starting at 90 mph (145 km/h) to 20 mph (30 km/h) while decelerating at 0.8 g.
6. Cool the brakes while driving 50 mph (80 km/h) for 3 minutes.
CAUTION:
• Do not come to a complete stop during the break-in procedure. This will imprint pad material onto the rotor,
causing a vibration during future use.
• Perform the break-in procedure in a safe location. FCA does not endorse speeding on public roads; therefore,
if a safe area cannot be used to achieve the speeds listed above, you must lower speeds to meet posted limits.
• Do not come to a complete stop when the system is hot and leave your foot on the pedal. Pad material will
immediately transfer to the rotor causing a vibration during future use.

Just wondering if anyone has ceramic brake pads/rotors on Q7 TDI? How long do they last and whats the good place to buy them? I dont have any experience with ceramic brakes but if they last longer, i would rather make that one time investment and not worry about brake pads and rotors. Thanks

Just wondering if anyone has ceramic brake pads/rotors on Q7 TDI? How long do they last and whats the good place to buy them? I dont have any experience with ceramic brakes but if they last longer, i would rather make that one time investment and not worry about brake pads and rotors. Thanks

That's a good question Sany. I'd like to know the same thing. I believe that carbon is pretty strong so I think they should last a long time.

Just wondering if anyone has ceramic brake pads/rotors on Q7 TDI? How long do they last and whats the good place to buy them? I dont have any experience with ceramic brakes but if they last longer, i would rather make that one time investment and not worry about brake pads and rotors. Thanks

Speculation on un-conventional concept/deployment is understandable. But if you browse our website regarding brake designs, you will get a better idea why RB brake's "un-conventional" designs are better (patented convergent vanes; open slots, and center-mount) and why our disc can run cooler than conventional designs (of traditional curved vanes and surface mount).

RB makes brake technology explainable and understandable, which is in turn proven on tracks - Feel free to check us out on Camaro, Corvette, GTR communities.

Same (material and design) merit on caliper rebuild components was presented to Porsche community w/o marketing data but based on the low heat transfer rate of SS pistons (vs. OE aluminum), and high temperature dust boots made of silicon (450F) vs. standard EPDM (300F). This option has effectively helped Porsche track drivers reduce the frequency of brake fluids replacement, improve the overall braking efficiency, and end the frustration of constant "cooked" dust boots (and just leave it as is).

I predicted and even guaranteed the result, after rebuilt with RB components your OE calipers will perform better and last much longer, than OE which I am sure there are hundreds of Porsche track enthusiasts can verify the validity of this claim.

I can only provide data based on the material basic and design merit which is what I learned from my old school (BSME) and discipline of my past profession that I believe in, as opposed to the marketing data which can be subjective and fabricated.

To learn the difference between the two (engineering and marketing), and how trustful a marketing data is, here is a good one from Brembo on CCM brakes.

One can simply deem it's true per claim (it's published by Brembo so who will question its validity?)

Or if one really want to interpret this marketing statement, one should READ into the number.

And in case you still have doubt, this table I prepared my be helpful.

As one member said earlier, this CCM/sintered pad is offered as an option only, believe it or not it's up to you. All info are presented based on the engineering data, and backed up by the fact of test result. Not a fiction or anything like some members kept throwing on us without a reason of his doubt, which is not a good thing to other members who want to learn something un-conventional Speculation on un-conventional concept/deployment is understandable. But if you browse our website regarding brake designs, you will get a better idea why RB brake's "un-conventional" designs are better (patented convergent vanes; open slots, and center-mount) and why our disc can run cooler than conventional designs (of traditional curved vanes and surface mount).

RB makes brake technology explainable and understandable, which is in turn proven on tracks - Feel free to check us out on Camaro, Corvette, GTR communities.

Same (material and design) merit on caliper rebuild components was presented to Porsche community w/o marketing data but based on the low heat transfer rate of SS pistons (vs. OE aluminum), and high temperature dust boots made of silicon (450F) vs. standard EPDM (300F). This option has effectively helped Porsche track drivers reduce the frequency of brake fluids replacement, improve the overall braking efficiency, and end the frustration of constant "cooked" dust boots (and just leave it as is).

I predicted and even guaranteed the result, after rebuilt with RB components your OE calipers will perform better and last much longer, than OE which I am sure there are hundreds of Porsche track enthusiasts can verify the validity of this claim.

I can only provide data based on the material basic and design merit which is what I learned from my old school (BSME) and discipline of my past profession that I believe in, as opposed to the marketing data which can be subjective and fabricated.

To learn the difference between the two (engineering and marketing), and how trustful a marketing data is, here is a good one from Brembo on CCM brakes.

One can simply deem it's true per claim (it's published by Brembo so who will question its validity?)

Or if one really want to interpret this marketing statement, one should READ into the number.

And in case you still have doubt, this table I prepared my be helpful.

As one member said earlier, this CCM/sintered pad is offered as an option only, believe it or not it's up to you. All info are presented based on the engineering data, and backed up by the fact of test result. Not a fiction or anything like some members kept throwing on us without a reason of his doubt, which is not a good thing to other members who want to learn something un-conventional which can save money and solve their brake issue.

As a disclaimer this RB sintered pad effect was proven on GM CCM rotors only so far; ST rotors are being tested and we expect to have a result in about two weeks. But not on pccb yet, due to different generations we are not able to to confirm whether our sintered pad can produce the same repairing effect to pccb.

We all agree testing is believing so we are ready to modify our existing sintered pad shape (ZR1/Z28) for 991 GT3 calipers (but the wear sensor connections must be disabled due to OE calipers are closed top), you just simply swap OE pad with RB sintered, calipers and rotors can remain unchanged.

In case this test resulting some further disc damage (must verified by us prior) due to pad incompatibility, we will replace them with RB-ST rotors (you paid for the usage of the original pccb), and if they work just tell other here.

Those (presumably having issues with their pccb) who like to help the community can call (714-871-6392) or PM us.